Abrasive flow finishing

[Robert Harris]

Don't draw too much from these numbers - they are on a specific head manifold 
combination.

Example - Ford exhausts suck but the intakes are almost too great where as 
chevy uniformly sucks.  Porting one using data from another can lead to 
disaster.  Same with these numbers.  For example, the exhaust doesn't change 
until high lift - which would choke off much of the flow increase seen on the 
intake.  The intake flow increase could actually cost power unless the engine 
was recammed to take advantage of it. Guess what I am saying, is the raw 
numbers without a lot of other numbers would make any power guess a guess.

If the first ingredient ain't Habanero, then the rest don't matter.
Other Obsessions: Ferro-Equinary , 1972 "Killer Whale" Mustang
Currently Interred in the Peoples Democratic Republic of California - Stalag 
Montclair
Puck da guns - ban Politicians!!!!!
Robert Harris <bob at bobthecomputerguy.com>


-----Original Message-----
From:	Tuck [SMTP:sldbrass at infi.net]
Sent:	Monday, December 01, 1997 7:09 PM
To:	diy_efi at efi332.eng.ohio-state.edu
Subject:	RE: Abrasive flow finishing

At 06:53 PM 12/1/97 -0500, you wrote:
>
>-> Well that looks like (on the intake side)a peak of a bit over 20%
>-> increase in flow.  Any idea what that translates to in terms of power
>-> output?
>
> No, that's not a 20% increase in flow.  It's a 20% increase in *peak*
>flow.  For an engine you're more interested in average flow.  Total up
>all the numbers and divide.

Before you rip me a new one, run the numbers yourself next time.  The
average increase in flow across the range is about 21.9%  Below is an added
column for percent change, so peak is actually more like 33 percent at the
bottom of the range, with a second smaller peak to about 24 percent at the
top.

             Intake
Lift	Before	After	Chg	Percent Change
.050	  35	  38	 3		8.57
.100	  59	  78	19		32.758
.150	  84	112	28		33.333
.200	114	145	31		27.19
.250	142	164	22		15.5
.300	164	191	27		16.5
.350	176	203	27		15.34
.400	182	218	36		19.78
.450	185	230	45		24.3
.500	188	233	45		23.9
.550	191	233	42		21.9895
.600	188	233	45		23.9

The question is still how much power does that translate to.  If the change
in air flow results in a linear increase in power there are significant
gains to be had from extrude honing of this particular manifold.

Of course I am interested in how it would affect a rather different beast,
namely a fuel injected rotary, a creature which has a distinctly different
torque curve than most reciprocating engines.  It's generally accepted (and
my own car seems to be an example) that increasing the port size on a
rotary costs you on the bottom end (demand isn't sufficient to keep port
speed high), but from this it would appear that the engine has better flow
throughout the range as a result of the polishing and "porting" as it were,
of the manifold.

And FWIW the injection system on Mazda rotaries is not throttle body
injection.


Justin "Tuck" Cordesman
SOLID BRASS-> Dancing with the devil in the pale moonlight.

The lips of a Strange Woman drip honey,
and her mouth is smoother than silk.
But her fate is bitter as wormwood...
sharp as a two edged sword.